This invention relates to a method in radio-therapy using an x-ray beam for treatment and an apparatus for using the method. More particularly, this invention relates to the technology of collimating, or "shaping," an x-ray beam for accurately delivering radiation to a preliminarily determined target region.
In radiotherapy such as in x-ray oncology, it is essential to deliver a precise amount of radiation, or dose, to a precisely defined region of a patient's body. Before a high-energy treatment machine is used to actually deliver the required radiation for treatment, therefore, it has been known to use a low-energy simulation machine preliminarily to determine exactly where the dose should be delivered and how it can be achieved.
After the target region has thus been determined but before the patient is actually treated by the high-energy machine, however, a scheme must be established on the basis of the data obtained on the target region whereby the high-energy radiation provided by the high-energy machine for the treatment can be properly collimated, or shaped, such that the dose will be received exactly in the target region determined preliminarily as described above. There are different ways to collimate, or shape, an x-ray beam, but practically all rely on the simple method of selectively blocking the beam by placing obstructions strategically in the radiation path. Since x-ray radiation is not visible, it has been known to place a visible light source at a position which is equivalent to the position of the x-ray source, to expose the patient to the visible light and to mark the region of interest.
Current collimator technology, as described above, is crude in that it allows depiction of the field by casting shadows, requiring wires, blocks and a so-called multi-leaf collimator to obstruct light.
A liquid crystal display device of a light transmitting type may be used to project an image drawn on the display device can be projected on the patient's body for marking the target region, but resolution of the image is limited by the pixel size and is generally poor and either a high-intensity light source must be used or the process must be carried out in a darkened room so that the image projected on the patient's body can be clearly observed.